Embodiments of the present invention relate to a support ring assembly to support a substrate in a process chamber.
In the processing of substrates, such as semiconductor wafers and displays, a substrate is placed in a process chamber and exposed to an energized gas to deposit or etch material on the substrate. A typical process chamber comprises process components that include an enclosure wall that encloses a process zone, a gas supply to provide a gas in the chamber, a gas energizer to energize the process gas to process the substrate, a substrate support, and a gas exhaust. The process chamber components can also comprise a process kit, which typically includes one or more parts that can assist in securing and protecting the substrate during processing, such as for example, substrate rings which are rings that are located about the periphery of the substrate, such as deposition rings, cover rings and shadow rings.
In physical vapor deposition (PVD) processes, a substrate ring comprising a deposition ring is provided about the periphery of the substrate. The deposition ring typically surrounds the substrate and has a lip or ledge that rests on the substrate support. The ring shields the sidewall surfaces and peripheral edge of the substrate support that would otherwise be exposed to the energized gas in the chamber, from deposition of process residues. Thus, the deposition ring reduces the accumulation of process residues on the support, which would eventually flake off and contaminate the substrate. The deposition ring can also reduce erosion of the support structure by the energized gas. Providing a deposition ring also lowers the frequency with which the support assembly requires cleaning, because deposition ring itself can be periodically removed from the chamber and cleaned, for example, with HF and HNO3, to remove process residues that accumulate on the ring during substrate process cycles.
However, certain processes, such as for example, tantalum PVD processes with their exposure to the energized gas in the chamber during processing, heats up the deposition ring. Typically, the deposition rings, such as for example aluminum oxide deposition rings do not exchange a sufficient amount of heat with their surroundings in the vacuum environment to lower the temperature of the rings to acceptable levels. Excessive heating of the deposition ring is detrimental, because thermal stresses between the deposition ring and process residues accumulated on the ring, result in the peeling or spalling of the process residues from the deposition ring, and resultant contamination of the substrate. Also, the hot deposition ring can create temperature gradients emanating from the periphery of the substrate, which change the temperature of the substrate or energized gas during processing. Yet another problem with conventional rings, such as aluminum oxide deposition rings, is that they erode during cleaning and refurbishment processes, reducing their lifetime. This is especially true when cleaning process residues that are chemically difficult to remove, such as for example, tantalum deposits formed on aluminum oxide rings.
Accordingly, it is desirable to have a substrate ring, such as a deposition ring, that does not excessively increase in temperature during the processing of substrates. It is furthermore desirable to have a substrate ring that is not excessively eroded during cleaning of the ring. It is furthermore desirable to have a substrate ring that can reduce the formation of excessively high temperature gradients during substrate processing.